Power supply arrangement suitable for use in telephone systems



941. R. F. STEHLIK 2,251,302

POWER SUPPLY ARRANGEMENT SUiTABLE FOR USE IN TELEPHONE SYSTEMS Filed Sept. 12, 1958 HOV /NVEN7'0R H FAA NK STEHL/K ATTORNEY Patented Aug. 5, 1941 unite-p stares m POWER SUPPLY ARBANGEMENI SUITABLE, FOR" USE IN TELEPHONE SYSTEMS Rudolph; F-rank- Stehlik, Antwerp; Belgium; as'e signer to Associated Telephone:-

8a: Telegraph:

Company, Chicago;.lll., a: corporation-of: Dela ltpplication September 12,

193 s; Serial'No; 229343 1 IngGreatcBr-itain Septemlier 212 SI Claims (Cl. 1 7 21- 737.)

'iS- -t0 provide-a compactipieceof equipment suitableforuse in connectingto the' mains without the needfor: batteries and thelike, and suitable also :for. use wvith eitherralternating or direct current; and forv a,- wide: variety of mains voltages.

Accordingto onelfeature Of the inventionin a power supply:arrangementasuitable for'use in a, telephonasystem; the convertingequipment is adaptable for, operation. by either alternating or direct current by the alteration of: the connections on a terminal block; the connections for direct current. operation bringing. into action a vibrator by, means" of; which: pulsating current isfed: to,=a transformer. which inlthe case of the connections for: alternating; current operation is fed directly: fromrthe" mains.

According; toanother: feature of the invention in a; power supply. arrangement suitable for use in a telephone system; the" commercial supplymains are connected to: atransformer the output of which-islrectified, aseparate winding on'the transformer being: employed to provide. ringing current.

Afurther featureof the invention. isRthat-in a power supply arrangement: suitable for use ina. telephone: system,. a vibrator; operated from= commercial direct currentisupply mains provides pulsating current: which is: fed to a transformer: to give alternating current of: the appropriate voltage which is; subsequently rectified tog-ive theedirect current-required forxoperating the tele-- phone equipment;

Therinvention will; be better understood from the f ollowing-i description of? a preferred :methodof carrying it intoieffect. which should be taken in conjunction with thesaccompanying drawing comprisingl'F- igs. 1;-3. Eigztl is a. circuit diagram otthecompl-ete powensupply unit, while Figs 2" and. 3 show respectively the connections which are made.on;the terminaliblock in the case of direct and alternating current respectively.

Considering firstlthe case'of direct current operation with a supply at 220 volts when the upper set of connections in Fig. 2 will apply, it will be seen that from the right-hand supply terminal the circuit extends by way of resistance RN] to terminal 8, thence by way of cross connections to terminal 6 and tapping point F on the primary of the" transformer" '1, while from the left-hand terminal' of the" supply the circuit extends over resistances R2 i and R3 in parallel; winding of the vibrator or 'pole changer PC, terminal 5; cross connection to terminal I andtapping point G of the-transformer? The coil of" the vibratorPG is energised in thiscircuit including thaportion FG' of thetransformer primary winding-and it attracts its armaturethere hy: shcrt-ci'rcuiti'ng itself so that the vibrating armature is releasedand then' engages-its bacle' contact and'ismaihtained in operation in-rwell'-- known manner. It will be appreciated that when the =vibrating armature engages its lower contact the left hand terminal of the supply i is extended direct'to tapping point" G; while when it engages" its: upper contact this terminal is extended to tappingpoint A. Phe primaryof 'the transformer thusoperatesona center tapped basis, the centerspoi'nt being the tapping point F which is'connected over resistanoe R l 0-- to' the right-hand supply terminal] In these-circumstances'due to the movement -of' the vibrating armature a pulsating current passes throug-h the primaryof'the transformer: and generates a suitable alternating current in the secondary.

It will be seen-that the" transformerhas two secondary windings oneoi 'which EJ is connected to earthand extends to terminal-BL from which ringing current issupplied to the telephone equipment. Theother 'secondary'winding KLM;

thc whole oi which i's connected upin this case bythe strapping of terminals"Itand it, extends? to a-fulll wave rectifier R: preferably of the dry contact 1 type whereby direct current is supplied to terminals- B and Erepresentingbatteryand earth respectively for the current supply to the exchange equipment. Theearth lead from the reotifierto terminal E includes a choke CH which is shunted by the two large capacity electrolytic condensers El and E2, the junction point ofthese condensers; being connected tb the battery; lead extending to terminal' B. This formsa smoothing arrangement in accordance with well-known principles,

Since in these circumstances the vibrator or" pole changer is in-constantoperation, it is desirable-that speeia1 mounting arrangements shall be provided'imorder to ensure that its operation shall not produce undue noise, since in the circumstances in which a private telephone exchange is often used, the unit might be mounted in a room in which quiet was essential. The obvious need is to enclose the unit in a soundproof casing but when this is done difficulties arise in providing for satisfactory heat dissipation without making the equipment unduly bulky. According to a subsidiary feature of the invention this difficulty is overcome by resiliently mounting the pole changer in a solid metal casting. By this means the noise of operation is practically eliminated and the casting permits the adequate dissipation of heat. The thickness and nature of the metal casting are important and it has been found that the best results are obtained when this is constructed of aluminium from to V2" thick.

It will be seen that when the-direct current supply has a voltage of 110 instead of 220, the strapping connections made on the terminal block are slightly different as shown in the lower portion of Fig. 2. The strapping of terminals I and 2 has the efiect of short-circuiting resistances R2 and R3 so that adequate current is provided at the lower voltage for maintaining the operation on the pole changer PC. Moreover terminal 5 is connected to terminal 6 and terminal 8 is connected to terminal It so that the portion of the primary of the transformer T which is used is the portion AF, the tapping point C being used as the centre point.

In order that the power-supply unit shall be capable of providing a heavy current in certain circumstances while having comparatively low no load losses, it is provided that when a heavy current is required, for instance when switches are stepping or when acall to another exchange has been set up, relay RD is operated by the connection of earth to the associated terminal and thereupon resistance RIO is short-circuited. By this means the unit is enabled to deliver a heavy current at need while the losses when the system is not in use are negligible. The condensers Cl and C2 connected across the supply with their junction point earthed are to prevent the equipment from having any deleterious effect on other consuming devices connected to the supply.

When the supply is alternating current, the connections on the terminal block are as shown in Fig. 3, the upper connections being made in every case and the lower connections in accordance with the voltage indicated. It will be seen that in this case the supply mains are connected straight through to the primary of the transformer, different tappings of which are employed in accordance with the mains voltage. It is desirable also in this case to employ only the portion KL of the secondary winding which feeds the rectifier and this is taken care of by strapping terminals I4 and [5. In these circum stances it will be appreciated that the vibrator is not set in operation and that the condensers CIC7 and resistances RI and R4R9 which are provided on the primary side for smoothing and blocking purposes are no longer required.

I claim:

1. In a telephone system power supply unit, a, transformer having a primary winding and secondary windings, a supply circuit adapted to be connected with a source of either direct or alternating current, circuit connections including at least a portion of said primary winding, a vibrator for alternately closing said circuit connections when the said supply circuit is connected to a source of direct current, and a terminal block whereby the said circuit connections may be altercd to short circuit said vibrator when said supply circuit is connected to a source of alternating current, output terminals, a rectifier bridge, one of said secondary windings connected to a circuit including said rectifier bridge and a pair of said output terminals whereby the alternating current induced in said one secondary winding is rectified to thereby provide a source of direct current at said pair of output terminals for satisfactory operation of telephone equipment, said other secondary winding connected in circuit with another of said output terminals to provide a source of alternating current satisfactory as a ringing current supply for telephone equipment.

2. In a telephone system power supply unit, a transformer primary winding, input terminals for connecting said unit to a commercial source of power of either direct or alternating current, a vibrator adapted for operation by direct current, a terminal block, circuit connections from said primary winding and said vibrator to said terminal block, said terminal block provided for jumpering said circuit connections to connect said vibrator and said primary winding to said input terminals to operate said vibrator and thereby feed a pulsating current to said primary winding when direct current commercial power is connected thereto and for jumpering said circuit connections to connect said primary winding to said input terminals direct to feed alternating current to said primary winding when alterating current commercial power is connected thereto, a two winding secondary for said transformer, output terminals, a rectifier bridge, one of said secondary windings and said rectifier bridge connected to said output terminals whereby the alternating current induced into said secondary winding from said primary winding by transformer action is rectified to supply said output terminals with direct current suitable for operation of telephone equipment, and the other winding of said an alternating current source for use as ringing current for telephone systems.

3. In a telephone system power supply unit, a transformer having a primary winding and a secondary winding, a vibrator, input terminals adapted to be connected to a source of direct current, an input circuit including said input terminals, said vibrator and said primary winding whereby said vibrator feeds a pulsating current through said primary winding when said input terminals are connected to a source of direct current, a resistance included in said circuit for reducing the current flowing through said primary winding, a rectifier bridge, an output circuit including said secondary winding and said bridge connected to a load requiring direct current, said rectifier bridge changing the alternating current induced into said secondary winding by transformer action into direct current, and means for automatically short circuiting said resistance to increase the current flowing in said primary winding when an increase direct current is required for said output circuit.

RUDOLPH FRANK STEI-ILIK. 

